On Tue, Oct 17, 2017 at 7:44 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> Encode an overlay inode as struct ovl_fh encoding of the real inode.
> Pure upper file handles are explicitly marked with a flag in ovl_fh
> header.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/overlayfs/copy_up.c | 18 +++++-----
> fs/overlayfs/export.c | 86 +++++++++++++++++++++++++++++++++---------------
> fs/overlayfs/namei.c | 12 ++++---
> fs/overlayfs/overlayfs.h | 10 +++++-
> 4 files changed, 85 insertions(+), 41 deletions(-)
>
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index 0a2c2c3743b1..9af3a6b62038 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -233,25 +233,21 @@ int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat)
> return err;
> }
>
> -struct ovl_fh *ovl_encode_fh(struct dentry *lower, bool is_upper)
> +struct ovl_fh *ovl_encode_fh(struct dentry *dentry, bool is_upper,
> + bool connectable)
> {
> struct ovl_fh *fh;
> int fh_type, fh_len, dwords;
> void *buf;
> int buflen = MAX_HANDLE_SZ;
> - uuid_t *uuid = &lower->d_sb->s_uuid;
> + uuid_t *uuid = &dentry->d_sb->s_uuid;
>
> buf = kmalloc(buflen, GFP_KERNEL);
> if (!buf)
> return ERR_PTR(-ENOMEM);
>
> - /*
> - * We encode a non-connectable file handle for non-dir, because we
> - * only need to find the lower inode number and we don't want to pay
> - * the price or reconnecting the dentry.
> - */
> dwords = buflen >> 2;
> - fh_type = exportfs_encode_fh(lower, buf, &dwords, 0);
> + fh_type = exportfs_encode_fh(dentry, buf, &dwords, connectable);
> buflen = (dwords << 2);
>
> fh = ERR_PTR(-EIO);
> @@ -296,12 +292,16 @@ static int ovl_set_origin(struct dentry *dentry, struct dentry *origin,
> int err;
>
> /*
> + * We encode a non-connectable file handle for non-dir, because we
> + * only need to find the lower inode number and we don't want to pay
> + * the price of reconnecting the dentry on lookup.
> + *
> * When lower layer doesn't support export operations store a 'null' fh,
> * so we can use the overlay.origin xattr to distignuish between a copy
> * up and a pure upper inode.
> */
> if (ovl_can_decode_fh(origin->d_sb)) {
> - fh = ovl_encode_fh(origin, is_upper);
> + fh = ovl_encode_fh(origin, is_upper, false);
> if (IS_ERR(fh))
> return PTR_ERR(fh);
> }
> diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
> index 9ec2fe659e38..47ef0302dbd3 100644
> --- a/fs/overlayfs/export.c
> +++ b/fs/overlayfs/export.c
> @@ -41,7 +41,8 @@ static bool ovl_is_pure_upper_or_root(struct dentry *dentry, int connectable)
> static int ovl_dentry_to_fh(struct dentry *dentry, struct fid *fid,
> int *max_len, int connectable)
> {
> - int type;
> + const struct ovl_fh *fh;
> + int len = *max_len << 2;
>
> /*
> * Overlay root dir inode is hashed and encoded as pure upper, because
> @@ -49,20 +50,27 @@ static int ovl_dentry_to_fh(struct dentry *dentry, struct fid *fid,
> * that root dir is not indexed, because root dentry is pinned to cache.
> *
> * TODO: handle encoding of non pure upper.
> + * Parent and child may not be on the same layer, so encode
> + * connectable file handle as an array of self ovl_fh and
> + * parent ovl_fh (type OVL_FILEID_WITH_PARENT).
> */
> if (!ovl_is_pure_upper_or_root(dentry, connectable))
> return FILEID_INVALID;
>
> - /*
> - * Ask real fs to encode the inode of the real upper dentry.
> - * When decoding we ask real fs for the upper dentry and use
> - * the real inode to get the overlay inode.
> - */
> - type = exportfs_encode_fh(ovl_dentry_upper(dentry), fid, max_len,
> - connectable);
> + fh = ovl_encode_fh(ovl_dentry_upper(dentry), true, connectable);
> + if (IS_ERR(fh))
> + return FILEID_INVALID;
>
> - /* TODO: encode an ovl_fh struct and return OVL file handle type */
> - return type;
> + if (fh->len > len) {
> + kfree(fh);
> + return FILEID_INVALID;
> + }
> +
> + memcpy((char *)fid, (char *)fh, len);
> + *max_len = len >> 2;
FYI, there are 2 bugs cancelling each other here.
memcpy should copy fh->len
and max_len should be round up to dwords from fh->len
I pushed a fix patch to branch ovl-nfs-export-v1
> + kfree(fh);
> +
> + return OVL_FILEID_WITHOUT_PARENT;
> }
>
> /* Find an alias of inode. If @dir is non NULL, find a child alias */
> @@ -171,24 +179,44 @@ static struct dentry *ovl_fh_to_d(struct super_block *sb, struct fid *fid,
> {
> struct ovl_fs *ofs = sb->s_fs_info;
> struct vfsmount *mnt = ofs->upper_mnt;
> - const struct export_operations *real_op;
> - struct dentry *(*fh_to_d)(struct super_block *, struct fid *, int, int);
> struct dentry *upper;
> + struct ovl_fh *fh = (struct ovl_fh *) fid;
> + int err;
>
> - /* TODO: handle decoding of non pure upper */
> - if (!mnt || !mnt->mnt_sb->s_export_op)
> - return NULL;
> + /* TODO: handle file handle with parent from different layer */
> + if (fh_type != OVL_FILEID_WITHOUT_PARENT)
> + return ERR_PTR(-EINVAL);
> +
> + err = ovl_check_fh_len(fh, fh_len << 2);
> + if (err)
> + return ERR_PTR(err);
>
> - real_op = mnt->mnt_sb->s_export_op;
> - fh_to_d = to_parent ? real_op->fh_to_parent : real_op->fh_to_dentry;
> - if (!fh_to_d)
> + /* TODO: handle decoding of non pure upper */
> + if (!mnt || !(fh->flags & OVL_FH_FLAG_PATH_UPPER))
> return NULL;
>
> - /* TODO: decode ovl_fh format file handle */
> - upper = fh_to_d(mnt->mnt_sb, fid, fh_len, fh_type);
> + upper = ovl_decode_fh(fh, mnt);
> if (IS_ERR_OR_NULL(upper))
> return upper;
>
> + /*
> + * ovl_decode_fh() will return a connected dentry if the encoded real
> + * file handle was connectable (the case of pure upper ancestry).
> + * fh_to_parent() needs to instantiate an overlay dentry from real
> + * upper parent in that case.
> + */
> + if (to_parent) {
> + struct dentry *parent;
> +
> + if (upper->d_flags & DCACHE_DISCONNECTED) {
> + dput(upper);
> + return NULL;
> + }
> + parent = dget_parent(upper);
> + dput(upper);
> + upper = parent;
> + }
> +
> /* Find or instantiate a pure upper dentry */
> return ovl_obtain_alias(sb, upper, NULL);
> }
> @@ -207,21 +235,25 @@ static struct dentry *ovl_fh_to_parent(struct super_block *sb, struct fid *fid,
>
> static struct dentry *ovl_get_parent(struct dentry *dentry)
> {
> - const struct export_operations *real_op;
> struct dentry *upper;
>
> /* TODO: handle connecting of non pure upper */
> if (ovl_dentry_lower(dentry))
> return ERR_PTR(-EACCES);
>
> + /*
> + * When ovl_fh_to_d() returns an overlay dentry, its real upper
> + * dentry should be positive and connected. The reconnecting of
> + * the upper dentry is done by ovl_decode_fh() when decoding the
> + * real upper file handle, so here we have the upper dentry parent
> + * and we need to instantiate an overlay dentry with upper dentry
> + * parent.
> + */
> upper = ovl_dentry_upper(dentry);
> - real_op = upper->d_sb->s_export_op;
> - if (!real_op || !real_op->get_parent)
> - return ERR_PTR(-EACCES);
> + if (!upper || (upper->d_flags & DCACHE_DISCONNECTED))
> + return ERR_PTR(-ESTALE);
>
> - upper = real_op->get_parent(upper);
> - if (IS_ERR(upper))
> - return upper;
> + upper = dget_parent(upper);
>
> /* Find or instantiate a pure upper dentry */
> return ovl_obtain_alias(dentry->d_sb, upper, NULL);
> diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
> index d5313fb02e73..4f20af22bd0b 100644
> --- a/fs/overlayfs/namei.c
> +++ b/fs/overlayfs/namei.c
> @@ -108,7 +108,7 @@ static int ovl_acceptable(void *mnt, struct dentry *dentry)
> * Return -ENODATA for "origin unknown".
> * Return <0 for an invalid file handle.
> */
> -static int ovl_check_fh_len(struct ovl_fh *fh, int fh_len)
> +int ovl_check_fh_len(struct ovl_fh *fh, int fh_len)
> {
> if (fh_len < sizeof(struct ovl_fh) || fh_len < fh->len)
> return -EINVAL;
> @@ -172,7 +172,7 @@ static struct ovl_fh *ovl_get_origin_fh(struct dentry *dentry)
> goto out;
> }
>
> -static struct dentry *ovl_decode_fh(struct ovl_fh *fh, struct vfsmount *mnt)
> +struct dentry *ovl_decode_fh(struct ovl_fh *fh, struct vfsmount *mnt)
> {
> struct dentry *origin;
> int bytes;
> @@ -412,7 +412,7 @@ int ovl_verify_origin(struct dentry *dentry, struct dentry *origin,
> struct ovl_fh *fh;
> int err;
>
> - fh = ovl_encode_fh(origin, is_upper);
> + fh = ovl_encode_fh(origin, is_upper, false);
> err = PTR_ERR(fh);
> if (IS_ERR(fh))
> goto fail;
> @@ -574,7 +574,11 @@ int ovl_get_index_name(struct dentry *origin, struct qstr *name)
> struct ovl_fh *fh;
> char *n, *s;
>
> - fh = ovl_encode_fh(origin, false);
> + /*
> + * We encode a non-connectable file handle for index, because the index
> + * must be unqiue and invariant of lower hardlink aliases.
> + */
> + fh = ovl_encode_fh(origin, false, false);
> if (IS_ERR(fh))
> return PTR_ERR(fh);
>
> diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
> index 66a6447a0c2a..75a8b10d4e10 100644
> --- a/fs/overlayfs/overlayfs.h
> +++ b/fs/overlayfs/overlayfs.h
> @@ -72,6 +72,11 @@ enum ovl_index {
> #error Endianness not defined
> #endif
>
> +/* The type returned by overlay encode_fh when encoding an ovl_fh handle */
> +#define OVL_FILEID_WITHOUT_PARENT 0xf1
> +/* The type returned by overlay encode_fh when encoding two ovl_fh handles */
> +#define OVL_FILEID_WITH_PARENT 0xf2
> +
> /* On-disk and in-memeory format for redirect by file handle */
> struct ovl_fh {
> u8 version; /* 0 */
> @@ -266,6 +271,8 @@ static inline bool ovl_is_opaquedir(struct dentry *dentry)
>
>
> /* namei.c */
> +int ovl_check_fh_len(struct ovl_fh *fh, int fh_len);
> +struct dentry *ovl_decode_fh(struct ovl_fh *fh, struct vfsmount *mnt);
> int ovl_verify_origin(struct dentry *dentry, struct dentry *origin,
> bool is_upper, bool set);
> int ovl_verify_index(struct dentry *index, struct vfsmount *mnt,
> @@ -341,7 +348,8 @@ int ovl_copy_up(struct dentry *dentry);
> int ovl_copy_up_flags(struct dentry *dentry, int flags);
> int ovl_copy_xattr(struct dentry *old, struct dentry *new);
> int ovl_set_attr(struct dentry *upper, struct kstat *stat);
> -struct ovl_fh *ovl_encode_fh(struct dentry *lower, bool is_upper);
> +struct ovl_fh *ovl_encode_fh(struct dentry *dentry, bool is_upper,
> + bool connectable);
>
> /* export.c */
> extern const struct export_operations ovl_export_operations;
> --
> 2.7.4
>
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